Rendering shadow in 3D scene has been a difficult problem and a continuing topic of interest in 3D computer graphics and real-time rendering. The most commonly used traditional method for generating real-time shadow is shadow mapping, which involves generating a depth map from the light perspective and performing a depth comparison in the main rendering pass. Shadow mapping is relatively fast to perform, and is applicable to generate dynamic shadows. However, many mobile graphical processing units (GPUs) do not implement traditional shadow mapping because of hardware and power limitations. For example, many GPUs that support the OpenGL ES 2.0 standard do not implement traditional shadow mapping. Traditional shadow mapping techniques also experience problems that are difficult to mitigate, such as shadow acne and perspective aliasing. When deploying the shadow mapping process to a rendering pipeline, the developer has to carefully tune many parameters such as the perspective transformation parameters, shadow map resolution, polygon offset, etc., making it a very difficult and time consuming task. These issues preclude the generation of a single set of parameters and for the depiction of shadows for all models and scenes, leading to a less scalable solution.
In recent years, numerous methods have been proposed to improve shadow mapping quality. While newer shadow mapping techniques can improve the quality of rendered shadows, these techniques also add complexity to the basic shadow mapping process, which makes rendering the shadows more difficult to perform with mobile and embedded platforms that often have lower processing capabilities and often rely on batteries that are depleted more quickly during intense processing. Consequently, improvements to 3D visualization techniques for rendering shadows in the graphical displays produced by mobile and embedded devices would be beneficial.